This invention concerns enhanced oil recovery processes involving a polymer flood. More particularly, the invention concerns a recovery involving a xanthan polymer flood. More particularly, the invention concerns a polymer floor recovery process wherein the biodegradation of the xanthan polymer is suppressed by the use of a chemically modified xanthan gum polymer.
The commercially available biopolymer xanthan, or xanthan gum, has been used in enhanced oil recovery processes as a polymer flood, and this procedure is well known in the art. A major problem concerning the use of of xanthan is that various microbes found in reservoirs have the ability to metabolize xanthan before its usefulness is completed. A prior art method of combatting this microbial attack is by the injection of a biocide into the reservoir formation. However, the use of a biocide leads to worker exposure to potentially harmful compounds. Further, the cost of the biocide adds to the general expense of the enhanced oil recovery process.
Accordingly, there exists an urgent need for a means to suppress or reduce the biodegradation of xanthan in a polymer flood process.